Buried, resilient pipes, such as polyethylene (PE) pipes are used extensively throughout the United States for natural gas transmission and distribution. Leaks in such pipes must be quickly attended to because of the risk of explosion since the fluid is both flammable and under pressure. With increasing natural gas consumption, pipeline repair has become increasingly important. Current procedures for repairing buried natural gas pipes require excavations both upstream and downstream of the damage, and isolation of the damaged section of pipe by stopping the flow of fluid on both sides of the damage. The damaged section may then be repaired or replaced.
Designation: F 1563-01 of the ASTM International defines “squeeze-off” as a technique used to control the flow of gas through a pipe by the compressing action of a mechanical, hydraulic or pneumatic device. Additionally, squeeze-off may be used, as recommended by the tool or pipe manufacturer, to reduce the flow of gas to an acceptable rate, and under certain conditions complete stoppage of flow may be obtained.
Gas Industry Standard, GIS/PL2-7:2006, further requires that squeeze-off shall be limited by a positive mechanical ‘stop’ capable of being interchanged or reset for the specified size ranges, and the squeeze-off tool shall be capable of being locked mechanically in the loaded position when squeeze-off is fully applied
In order to expedite the excavation of pipe access holes or trenches, such holes or trenches are kept relatively small, especially when large digging equipment is unavailable. Access to the tube or pipe to be squeezed-off or crushed is therefore generally from the top or side thereof, and it is advantageous to employ squeeze-off tools which may be installed and withdrawn by a single operator; that is, tools which are relatively light and maneuverable, yet are capable of reversibly squeezing off pipes having diameters as large as 4 in. in which a fluid, such as a pressurized gas or liquid is flowing.